"Are blinds worth it?" usually means one of two things: are blinds worth having at all, or is made-to-measure worth paying for over a cheap ready-made one. Here is an honest answer to both.
What a blind actually gives you
A blind does several jobs at once: it controls light, gives privacy, cuts glare on screens, takes the edge off summer heat and winter chill, and finishes a window. For most rooms it is the simplest single way to make a window both practical and presentable, and a made-to-measure blind that fits properly will do all of that for years. On that basis, yes - blinds earn their keep.
Made-to-measure vs ready-made
Ready-made blinds are cut to standard sizes and sold off the shelf or trimmed at home. They are cheaper up front and fine for a standard window where one of the stock sizes happens to fit. The catch is fit: few windows match a stock size exactly, so a ready-made often leaves gaps, needs cutting down (which not all types allow), or simply looks approximate. The choice of fabric, colour and type is also far narrower.
Made-to-measure blinds are cut to your exact opening, so they fit cleanly, screen light properly at the edges, and come in the full range of fabrics, colours and styles. They cost more than a basic ready-made, but less than most people expect, and the fit is the difference between a window that looks finished and one that looks made-do.
When ready-made is fine
A standard-sized window, a rental where you want something cheap and temporary, or a low-priority room can all be served well by a ready-made blind - especially a simple roller.
When made-to-measure is worth it
Any non-standard window, anywhere darkness or a tight fit matters (bedrooms, especially), a particular colour or fabric, or a room you want to look properly dressed - these are where made-to-measure pays for itself. And because the same made-to-measure blind varies in price between retailers, comparing first keeps the cost closer to ready-made than you would think.